(1) Field of the Invention
This invention relates to gearing and more particularly to a differential type gear transmission having plural power paths from its input to output, to achieve a variable speed transmission.
(2) Description of the Prior Art
Variable speed transmissions have been a perplexing problem of machine elements. By variable speed transmission in this context it is meant a machine element that will transmit power from one rotating shaft to another at varying ratios of speed between the two shafts. Specifically, excluded from this are the choice of different speeds such as where the speed ratio is chosen between different steps regardless of how many steps are included.
In commercial use today the main variable speed transmissions are by V-belt drives where the effective sheave diameter of one or both sheaves are changed.
However, an effective commercial transmission which transmits power through toothed gears with variable speed has not been achieved. There has been suggested that a planetary gear could be used wherein one of the gears is braked rather than either permitted to run free or being locked in a fixed position. Such a system, to some degree, will achieve a variable speed transmission. However, it is at the sacrifice of being inefficient in the loss of energy in the brake.
Before this application was filed, a search was made in the U.S. Patent and Trademark Office and the following patents were found in this search.
Jacono U.S. Pat. No. 3,429,394 PA1 Tormolen U.S. Pat. No. 3,394,620 PA1 Horvath U.S. Pat. No. 3,220,284 PA1 Thompson U.S. Pat. No. 1,274,627
According to the applicant's understanding of these patents that Thompson, Jacono and Horvath are primarily concerned with the braking type speed control. The Tormolen also embodies a planetary gear system wherein the housing moves axially along the input and output shafts. The position of the housing controls the settings and different parts and, therefore, controls different speeds.